Grassroots Health and ZRT Labs are working together to help us all make sure we have enough vitamin D. Participate in understanding vitamin D. Visit grassrootshealth.net and join the research project. You'll get your D tested twice a year for five years. The cost is just $40 a test, $80 a year, more than reasonable for accurate D testing, and you'll help provide real answers, for yourself and for us all, about how much D we get and how much we need. Join now. Do commit to the full 5 years if you decide to sign on. If not joining for the full test period please use the testing links below.